Shrinkproofing wool



Patented Apr. 10, 1951 UNITED STATES No Drawing. Application July 6,1949,

Serial No. 103,320

- 4 Claims. 101. 8-128) The invention relates to an improved method ofshrink-proofing wool, and to the improved product of such treatment.

Heretorore, the only economical methods for shrink-proofing wool bycontrolled damage processes have involved the use of chlorine or otherhalogen in various ways. While good shrinkage control will be the resultif the method is carefully regulated as to pH, concentration, time oftreatment, etc., there are certain disadvantages in its use that havenot been overcome.

First, the chlorine or other halogen is disagreeable to handle and isinjurious to the health or" the workmen; secondly, it is highlycorrosive; thirdly, there are side reactions taking piece in its usethat damage the wool and yet do not aid shrink-proofing, and whichinvolve the formation of chloramines: fourth, the problem of tailing isa big one because of the high reactivity of the chlorine with wool; Uh,chlorine treatment is somewhat expensive; and lastly, uniformpenetration of the chlorine or chlorinating agent cannot be expectedbecause the halogen has such a strong amnity for W001 that completeexhaustion of the bath occurs rapidly.

The actual shrink-proofing of wool with chlorine or other halogenaccording to one theory is not caused by a direct union of halogen withthe wool molecule, but because the halogen is a very strong oxidizingagent the cystine linkages of the wool molecule are oxidized'and broken,which changes the expanding, contracting and frictional characteristicsof the fiber.

-It is known that dilute solutions of potassium permanganate KMnO4) willreduce only slightly the felting characteristics of wool and as early as1907 it was proposed by Kammerer to treat wool with permanganic acid,which is a much stronger oxidizing agent than KMnOr, and effectshrink-proofing. This method and any method involving the use of thepermanganate ion at or below 100 C. does not produce a wool possessingsatisfactory characteristics. The reasons for this are that thereactions are mainly only surface reactions and do not penetrate to anyconsiderable extent within the fiber. Any real penetration can only beachieved at this or lower temperatures by sacrificing the natural feelor handle of the wool. An objectionable scroop results and the fiber isstifi and useless. Further, different grades of wool display differentdegrees of shrinkproofing because of variations in the thickness of thevarnish-like covering on the cuticle as revealed by the electronmicroscope.

It is an object of the present invention to im- FATENT UFFICE.

prove the method of shrink-proofing wool by subjecting'the wool to atreatment that can be controlled easily and that produces a wool whichretains its natural feel and strength without appreciable loss ofweight.

Further, it is an object of this invention to produce a more leveldyeing wool. I have discovered that speedy penetration of the wool fiberby a solution of potassium permanganate or other suitable oxidizingagent can be effected by subjecting wool to superatmospherictemperatures and pressures in an autoclave in very dilute solutions ofKMnOr, with or without the aid of buffers, as for instance MgSOa.

The wool under pressure is rapidly hydrolyzed at the cystine linkage asfollows:

Molecular structure of wool H "H hydrogen bond l\ r C311 /CHH side chainC3 C O NH N CR CHR C O C Ne NH /OHR O O 0 H3i\' RHC\ salt linkage 03 C ONH N Cystine linkage hydrolysis R-S-S-R, R-SH HOS-R1 H25 produced actsas a reducing agent and also splits the cystine linkage s ms R-S-S-RzRSH HSR As KMnO4 is also present, the H28 is oxidized ZHQS 30: 2501 $520-l H3803 HZS is a very feeble acid and the H28, H280: and H2804 allreact within the fiber and at the surface withKMnOr to produceipermanganic acid. Permanganic acid is a powerful oxidizing compound butis only produced where KMnOr comes in contact with wool, therebyproducing a smooth, non-harsh wool. No H28 is detectable on the woolafter pressure treatment in this manner, which is not the case withpressure alone in the absence of oxygen or oxidizing compounds.

The hydrolyzed cystine group is oxidized as follows:

There is also a breaking of the cystine linkage by oxidation HIMDO;

CHrS-S-CH CH;SO3H HOgSCHr KMlnO4 also does this but is not aspredominant as the I-IMnO; at the fiber surface and within the fiberKMnO;

A permanent set is also imparted to the wool fiber by heat and asfollows:

The hydrolyzed cystine groups are joined by oxidation oxidation n-snrasn R-S-Rr Also at elevated temperatures the disulfide bonds of keratinare disrupted. The thiosulfonic acids thus formed react with free aminogroups in the keratin to build R-SNH-R' linkages, thus imparting apermanent set to the wool.

Condensation between an amino group of a basic side chain and an -SI-Igroup formed by hydrolysis of S--S- linkages also occurs.

The hydrolysis of --S-S yields the -SOH going to H2S+--CI-IO,condensation of CI-IO with NI-lz yields NI-l--CI-I.

All the above phenomena are accompanied by a disarrangement of thesurface layers, of the cuticle and under the cuticle and a reduction inthe differential friction effect, rendering the fiber resistant tofelting.

The increased luster and strength is due to the fact that the scalycovering fuses into a more compact and regular surface. The resultingwool has no loss in strength and has a soft and desirable feel.

Further, the method bleaches the wool and gives a product of superiorand more level dyeing characteristics. In other words, the methodcombines the usual bleaching treatment with a shrink-proofing treatment.

After the pressure treatment, the brown manganese hydrate is removedwith NaHSOa followed by NazCO; and washing.

Advantages of the process are as follows:

1. It is not injurious to health of operators as are the halogens andH202.

2. The process does not require large concentrations of chemicals.

3. The process can be performed in a short time.

4. The process results in very even treatment by penetrating the fiber.

5. It is not necessary to control the pH because the process is carriedout under essentially neutral conditio s.

6. It is no 5* to over treat.

'7. One ca .ach as well as shrink-proof.

8. The product is soft and lofty handle.

9. The process is very economical.

10. Excess acids produced are neutralized by KOH present from. KMnO4.

4' of the manner in which the treatment may be carried into efiect:

Example 1 Virgin wool 60-64s grade yarn was treated with a solution of250 mg. KMnoi to two liters of water (.0l25%) in an autoclave at 15 lbs.superatmospheric pressure for five minutes. This was followed by atreatment with a dilute solution of NaHSOa to remove manganese hydrateand then to a dilute solution of NazCOs. The treated wool was completelyshrink-proofed. Untreated wool shrank 25%.

Example 2 Virgin wool yarn s grade was treated with a solution of 100mg. KMnO4 in two liters of water (.005%) in an autoclave at 15 lbs.superatmospheric pressure for five minutes. This wool was completelyshrink-proofed. Untreated wool shrank 40%.

Example 3 70s grade yarn was treated with a solution of 250 mg. KMI104to two liters of water (.0125%) in an autoclave at 10 lbs.superatmospheric pressure for five minutes. The wool was completelyshrink-proofed. Untreated wool shrank 40%.

Example 4 70s grade yarn was treated with a solution of 250 mg. KMnOr totwo liters of water (.0125%) in an autoclave at 5 lbs. superatmosphericpressure for five minutes. The wool shrank about 4% because of the lowerpressure used but still was fairly well shrink-proofed. Seven minutes at5 lbs. produced a completely shrink-proofed wool. Untreated wool shrank40%.

Example 5 Woolen socks 60s-64s grade was treated in .05% KMI104 solutionfor ten minutes at 15 lbs superatmospheric pressure in an autoclave.This Was followed by treatment with a dilute 5% solution of NaI-ISO: andthen with NazCOa to neutralize the acidity and the treated goods werethen washed thoroughly. Untreated socks shrank 30% after thirtylaunderings, and treated socks exhibited no felting shrinkage. This wasa strong anti-shrinking treatment.

The yarns treated in the above examples were dried and cut into fourinch lengths and the tips cemented with cellulose acetate and shaken ina .5% Na2COa.lO H2O solution for fifteen minutes. The shaker made 2'76completed (back and forth) strokes per minute. In shrink-proofing enoughKMnO4 should ordinarily be used so that the bath has a permanganatecolor at the end of treatment. This insures an oxidation reactionthroughout.

In shrink-proofing wool it is sometimes desirpressure may be used.Larger concentrations may be desirable where considerable bleach is Thefollowing specific examples are illustrative also desired. However, Iprefer lower concentrations of KMnOi with the lower limit in theneighborhood of 001% and the upper limit to be determined by the damagedone to the wool. This upper limit may be around 0.1% except for shorttimes of treatment.

A combination of unshrinkable wool with untreated fibers of all typespermits the production of two-tone effects as well as novelty or blistereffects and difierently dyed fabrics.

While in the above description potassium permanganate has been referredto as the preferred oxidizing agent, other oxidizing agents may besubstituted for the permanganate either in whole or in part, withoutdeparting from the spirit of the invention considered in its broadestaspects, although, as previously set forth, potassium permanganate ispreferred. Where other oxidizing agents are employed the quantityemployed should be such as to be the equivalent of the proportion ofpermanganate herein set forth.

In some instances it has been found desirable to give the wool apreliminary treatment with an oxidizing agent other than KMnO4, such asan alkaline or acid permanganate, oxygen, ozone, hydrogen-peroxide,organic peroxides, halogenated organic compounds, KzCIzOl, and the like,with or without catalysts, followed by a treatment with potassiumpermanganate. These and other oxidizing agents used either singly or incombination may be used in addition to or in place of the permanganatein the main treating step.

I claim:

1. A process of shrink-proofing wool which comprises treating the woolfor a short period of time in a closed chamber under superatmosphericrange of 5 to 15 pounds per square inch.

MAYNE R. COE, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

FOREIGN PATENTS 25 Number Country Date 5,612 Great Britain 1907 569,730Great Britain June 6, 1945 586,020 Great Britain Mar. 4, 1947 603,379Great Britain June 15, 1948 OTHER REFERENCES Frolich: WollkundeTechnologie Der Textilfasern, Bd. VIII, Teil 1, J. Springer, Berlin,1929, pages 314-323. (Book in Dept. Agric. Library.)

1. A PROCESS OF SHRINK-PROOFING WOOL WHICH COMPRISES TREATING THE WOOLFOR A SHORT PERIOD OF TIME IN A CLOSED CHAMBER UNDER SUPERATMOSPHERICPRESSURE CONDITIONS AND AT A TEMPERATURE ABOVE 100* C. WITH AN ALKALIMETAL PREMANGANATE IN AQUEOUS SOLUTION, THE STRENGTH OF THE PERMANGANATEEMPLOYED BEING WITHIN THE RANGE OF .001 TO .1%.